Abstract: For the problem that dirt on surface of power transmission line's insulator of power system could cause flashover and lead to braking and power-off, the paper introduced a design scheme of remote monitoring system of leakage current of power transmission line's insulator based on dirt-flashover principle and relationship of dirt degree and leakage current of power transmission line's insulator. The system uses GSM wireless communication method and can realize on-line and remote transmission function for monitored data. Long-term running results on 500 kV, 220 kV and 100 kV high-voltage lines showed that the system is stable in performance and reliable in monitoring data.